The effect of age and sex on facial mimicry: a three-dimensional study in healthy adults

Quantified analysis of facial movement: A reference for clinical applications

Most techniques for evaluating unilateral impairments in facial movement yield subjective measurements. The objective of the present study was to define a reference dataset and develop a visualization tool for clinical assessments. In this prospective study, a motion capture system was used to quantify facial movements in 30 healthy adults and 2 patients. We analyzed the displacements of 105 reflective markers placed on the participant's face during five movements (M1-M5). For each marker, the primary endpoint was the maximum amplitude of displacement from the static position (M0) in an analysis of variance. The measurement precision was 0.1 mm. Significant displacements of markers were identified for M1-M5, and displacement patterns were defined. The patients and age-matched healthy participants were compared with regard to the amplitude of displacement. We created a new type of radar plot to visually represent the diagnosis and facilitate effective communication between medical professionals. In proof-of-concept experiments, we collected quantitative data on patients with facial palsy and created a patient-specific radar plot. Our new protocol for clinical facial motion capture ("quantified analysis of facial movement," QAFM) was accurate and should thus facilitate the long-term clinical follow-up of patients with facial palsy. To take account of the limitations affecting the comparison with the healthy side, we created a dataset of healthy facial movements; our method might therefore be applicable to other conditions in which movements on one or both sides of the face are impaired. The patient-specific radar plot enables clinicians to read and understand the results rapidly.

The Average Facial Expressions: A Range of Motion Analysis for Different Sex and Age Groups

Facial expressions are ubiquitous in communication. Therefore, assessment of mimic function is essential in facial surgery, but no reference standards are currently available. This prospective study aims to create reference values of three-dimensional landmark displacement for different sex and age groups.

Methods

Three-dimensional photographs were taken from healthy subjects in rest, maximum closed smile, and pouting. Displacement for both exercises of perioral landmarks was analyzed with MATLAB as absolute displacement and as the ratio of mouth width. Additionally, displacement in three planes was analyzed for each landmark. Averages were calculated for both genders in four age groups: 4-8, 8-12, 12-16, and >16 years.

Results

In total, 328 subjects were included. Oral landmarks predominantly moved forward and backward for both exercises. Nasal landmarks predominantly moved vertically. Growing up, oral landmark displacement decreased for smiling, whereas nasal landmark displacement increased. For pouting, oral landmark displacement increased while growing up, whereas nasal landmark displacement decreased.

Conclusions

The present study creates reference values for movement of perioral structures for different sex and age groups, for two facial expressions. These data are of great value for the assessment of mimic function and give insight into the development of facial animation over time.

Smile dimensions affect self-perceived smile attractiveness

Facial expressions play a leading role in human interactions because they provide signaling information of emotion and create social perceptions of an individuals’ physical and personality traits. Smiling increases socially perceived attractiveness and is considered a signal of trustworthiness and intelligence. Despite the ample information regarding the social importance of an attractive smile, little is known about the association between smile characteristics and self-assessed smile attractiveness. Here we investigate the effect of smile dimensions on ratings of self-perceived smile attractiveness, in a group of 613 young adults using 3D facial imaging. We show a significant effect of proportional smile width (ratio of smile width to facial width) on self-perceived smile attractiveness. In fact, for every 10% increase in proportional smile width, self-perceived attractiveness ratings increased by 10.26%. In the present sample, this association was primarily evident in females. Our results indicate that objective characteristics of the smile influence self-perception of smile attractiveness. The increased strength of the effect in females provides support to the notion that females are overall more aware of their smile and the impact it has on their public image.

Assessment of orofacial dysfunction using the NOT-S method in a group of Turkish children with cerebral palsy

OBJECTIVES

A healthy determination of orofacial findings of children with cerebral palsy is important as this will lead us to utilize perfect multidisciplinary therapies of orofacial dysfunctions (OFD). Nordic Orofacial Test-Screening (NOT-S) is a comprehensive screening method of OFD which consists of a structured interview and clinical examination. The aim of our study was to evaluate the orofacial dysfunctions in a group of Turkish children with cerebral palsy using Nordic Orofacial Test-Screening (NOT-S) and find out the factors associated with OFD comparatively with a healthy group.

MATERIALS AND METHODS

NOT-S was applied to 84 children aged 3-16 years. Forty-two children with cerebral palsy were included in the study group and 42 healthy children were randomly selected for the control group. Two trained and calibrated examiners who were experienced on NOT-S interview and examination of the validity and reliability of the Turkish version performed screening and interpreted the results.

RESULTS

NOT-S interview and clinical examination subscale scores of children with cerebral palsy were higher and found to be statistically significant (Mann-Whitney U test; p < 0.001). The total scale score of the cerebral palsy group was also statistically significant (p < 0.001). The most common dysfunctions were in the facial expression area (55.9%) and in the chewing and swallowing area (52.4%) following in sensory function area (47.6%).

CONCLUSIONS

The results of this study indicated that the NOT-S protocol was an effective and valuable tool for the comprehensive screening of orofacial dysfunctions in a group of Turkish children with cerebral palsy.

Functional decline in facial expression generation in older women: A cross-sectional study using three-dimensional morphometry

Elderly people show a decline in the ability to decode facial expressions, but also experience age-related facial structure changes that may render their facial expressions harder to decode. However, to date there is no empirical evidence to support the latter mechanism. The objective of this study was to assess the effects of age on facial morphology at rest and during smiling, in younger (n = 100; age range, 18-32 years) and older (n = 30; age range, 55-65 years) Japanese women. Three-dimensional images of each subject's face at rest and during smiling were obtained and wire mesh fitting was performed on each image to quantify the facial surface morphology. The mean node coordinates in each facial posture were compared between the groups using t-tests. Further, the node coordinates of the fitted mesh were entered into a principal component analysis (PCA) and a multifactor analysis of variance (MANOVA) to examine the direct interactions of aging and facial postures on the 3D facial morphology. The results indicated that there were significant age-related 3D facial changes in facial expression generation and the transition from resting to smiling produced a smaller amount of soft tissue movement in the older group than in the younger group. Further, 185 surface configuration variables were extracted and the variables were used to create four discriminant functions: the age-group discrimination for each facial expression, and the facial expression discrimination for each age group. For facial expression discrimination, the older group showed 80% accuracy with 2 of 66 significant variables, whereas the younger group showed 99% accuracy with 15 of 144 significant variables. These results indicate that in both facial expressions, the facial morphology was distinctly different in the younger and older subjects, and that in the older group, the facial morphology during smiling could not be as easily discriminated from the morphology at rest as in the younger group. These results may help to explain one aspect of the communication dysfunction observed in older people.

Juvenile Facial Growth and Mimicry: A Preliminary 3D Study

Studies focused on facial development during childhood have been conducted by means of 3D technology to provide modifications of anthropometric parameters. Facial mobility was also considered. This study proposed a 3D approach to facial growth changes. Facial surface data of 6 subjects were acquired in T1 (age 7-14 years) and after 7 years (T2), in rest position, and during voluntary movements, by a 3D laser scanner. Linear and angular measurements on rest position scans at T1 and T2 were compared. Each mimic scan was superimposed with the corresponding rest scan. Displacement of significant anthropometric points was measured for each facial gesture and at T1 and T2 statistically compared. Vertical measurements were those most influenced by aging. Some measurements of central facial area were consistent over time. The pattern of soft tissues displacement for each expression was consistent in T1 and T2. These results may be helpful for missing children identification.

Gender-Affirming Hormone Treatment Induces Facial Feminization in Transwomen and Masculinization in Transmen: Quantification by 3D Scanning and Patient-Reported Outcome Measures

INTRODUCTION

Hormone treatment induces feminization of the body in transwomen and masculinization in transmen. However, the effect of hormone treatment on facial characteristics is still unknown.

AIM

We aimed to study whether hormone treatment induces facial feminization and masculinization and how this potential change affects satisfaction and self-esteem.

METHODS

In this single-center cohort study, we included 27 transwomen and 15 transmen who received standardized hormone treatment in the Center of Expertise on Gender Dysphoria, VU University Medical Center Amsterdam. Facial 3-dimensional images were obtained at baseline and at 3 and 12 months. At each image, 22 facial landmarks were placed. Furthermore, the FACE-Q Satisfaction with Facial Appearance Overall and the Rosenberg self-esteem scale were obtained at the same measurement points.

MAIN OUTCOME MEASURES

The main outcome measures included the relative local shift of skin in millimeters in the 22 landmarks in the transverse (x-axis), coronal (y-axis), and sagittal (z-axis) anatomic axes, the color maps, and the outcomes of the questionnaires.

RESULTS

After 12 months, cheek tissue in transwomen increased, with 0.50 mm (95% CI 0.04-0.96) in the x-axis and 1.08 mm (95% CI 0.31-1.85) in the z-axis. Tissue in the jaws decreased with -0.60 mm (95% CI -1.28-0.08) in the x-axis and -0.18 mm (95% CI -0.03-0.33) in the y-axis. Cheek tissue in transmen decreased with -0.45 mm (95% CI -1.00-0.11) in the x-axis and -0.84 mm (95% CI -1.92-0.25) in the z-axis. These changes already started after 3 months. An increase in satisfaction with the facial appearance was found in both transwomen and transmen. There were no changes in reported self-esteem.

CLINICAL IMPLICATION

These results could lead to more realistic expectations of facial changes. Furthermore, our results suggest that the face continues to change for at least a year, which could suggest that performing facial feminization surgery after 1 year of hormone treatment might be too early.

STRENGTH & LIMITATIONS

This study is the first that provides insight into the facial changes in transgender individuals receiving hormone treatment, and it introduces an objective method to examine (small) facial changes. Our study is limited by the poor reliability of the landmarks, the difficulty of facial fixation, and the lack of gender-specific questions in the questionnaires.

CONCLUSIONS

Hormone treatment in transwomen induces an increase in cheek tissue and a decrease in jaw tissue. In transmen a tendency of decrease in cheek tissue and an increase in jaw tissue was found. These changes are in the direction of the desired gender. Tebbens M, Nota NM, Liberton NPTJ, et al. Gender-Affirming Hormone Treatment Induces Facial Feminization in Transwomen and Masculinization in Transmen: Quantification by 3D Scanning and Patient-Reported Outcome Measures. J Sex Med 2019;16:746-754.

Three-dimensional longitudinal evaluation of facial mimicry in orthognathic class III surgery

The effect of bimaxillary orthognathic surgery on facial mimicry was assessed longitudinally in 15 patients with dentoskeletal class III facial dysmorphism (seven men, eight women, mean age 28 years). The patients were analysed pre-surgery and at 6, 12, and 24 months post-surgery while performing verbal (five vowels) and non-verbal (open and closed mouth smile, lip purse) soft tissue facial movements. The three-dimensional motions of right and left nasogenian, crista philtri, cheilion, and lower lip landmarks were detected by an optoelectronic instrument, and a total mobility index was obtained. Differences between the sides were quantified by the symmetry index. Patient values were compared to those collected previously from healthy volunteers by computing z-scores. On average, no significant differences were found in the mobility of the buccal soft tissues at 24 months after surgery (ANOVA P-value, range 0.075-0.808), with positive median z-scores (pooled mean value close to 0.6). Symmetry indices ranged around the control reference values, showing no stage-related differences (Friedman test P-value, range 0.252-0.937), and exceeding 90% for all movements at 24 months after surgery. Bimaxillary osteotomy does not compromise facial mimicry in either verbal or non-verbal facial movements.

Variability of facial movements in relation to sexual dimorphism and age: three-dimensional geometric morphometric study

The aim of this study was to introduce suitable imaging technique and analytical methods for a detailed description of the facial movements in relation to sexual dimorphism and age in adult individuals. Removing of size factor from the analysis, we hypothesised that there will be no significant intersexual difference in facial mobility. We assume facial movements to be more pronounced in the older age category due to increasing the facial surface. We have compared five facial movements - raising eyebrows, closing eyes, pursing of the lips, inflating of the cheeks and smile - in relation to neutral expression of the human face. The material sample comprised three-dimensional facial surface models of healthy adult individuals of the Czech nationality (63 females, 58 males). Methods of geometric morphometry and multivariate statistics were used. Local tissue motion due to facial movements was expressed using colour-coded maps. The movement showing significant intersexual difference was inflating of the cheeks. Ageing in both sexes has significantly influenced the facial mobility on average after 50 years of age. Changes related to senescence have occurred in eye closing, smile and inflating of the cheeks. An enlarged facial surface has been noted in the group of individuals belonging to the older age category, what is probably the result of increased manifestation of skin folds and wrinkles. This is related to the loss of skin elasticity and overall weakening of the underlying muscles, especially in the infraorbital and cheeks area.

Sexual dimorphism in human facial expressions by 3D surface processing

Human face is a dynamic system where facial expressions can rapidly modify geometry of facial features. Facial expressions are believed to be universal across world populations, but only a few studies have explored whether grimacing is sexually dimorphic and if so to what extent. The present paper explores inter- and intra-individual variation of human facial expressions with respect to individual's sex based on a set of neutral and expression-varying 3D facial scans. The study sample composed of 20 individuals (10 males and 10 females) for whom 120 scans featuring grimaces associated with disgust, surprise, "u" sound, smile and wide smile were collected by an optical scanner Vectra XT. In order to quantify the dissimilarity among 3D images, surface comparison approach based on aligned 3D meshes and closest point-to-point distances was carried out in Fidentis Analyst application. The study revealed that sexual dimorphism was indeed one of the factors which determined the extent and characteristics of facial deformations recorded for the studied expressions. In order to produce a grimace, males showed a tendency towards extending their facial movements while females were generally more restrained. Furthermore, the facial movements linked to the wide smile and "u" sound were revealed as the most extensive relative to the other expressions, while the smile and surprise were shown indistinguishable from the neutral face.

Use of autonomous maximal smile to evaluate dental and gingival exposure

Objective

This study was performed to validate the autonomous maximal smile (AMS) as a new reference for evaluating dental and gingival exposure.

Methods

Digital video clips of 100 volunteers showing posed smiles and AMS at different verbal directives were recorded for evaluation a total of three times at 1-week intervals. Lip-teeth relationship width (LTRW) and buccal corridor width (BCW) were measured. LTRW represented the vertical distance between the inferior border of the upper vermilion and the edge of the maxillary central incisors. Intraclass correlation coefficients (ICCs) for reproducibility, and the m-value (minimum number of repeated measurements required for an ICC level over 0.75), were calculated.

Results

LTRW and BCW of the AMS were 1.41 and 2.04 mm, respectively, greater than those of the posed smile (p < 0.05), indicating significantly larger dental and gingival exposure in the AMS. The reproducibility of the AMS (0.74 to 0.77) was excellent, and higher than that of the posed smile (0.62 to 0.65), which had fair-to-good reproducibility. Moreover, the m-value of the AMS (0.88 to 1.05) was lower than that of the posed smile (1.59 to 1.85).

Conclusions

Compared to the posed smile, the AMS shows significantly larger LTRW and BCW, with significantly higher reproducibility. The AMS might serve as an adjunctive reference, in addition to the posed smile, in orthodontic and other dentomaxillofacial treatments.

Assessing Normal Smiling Function Through 3D-3D Surfaces Registration: An Innovative Method for the Assessment of Facial Mimicry

Smiling has a great importance, both from a functional and an aesthetic point of view. The introduction of modern 3D acquisition and elaboration methods may provide additional help in the evaluation of facial mimicry. This study aims at proposing an innovative method to assess facial and labial movements in different types of smiles. Twenty healthy subjects (10 males, 10 females, mean age 27.5 years, SD 4.5 years), were recorded through a stereophotogrammetric system in neutral position and in three types of smiles: Mona-Lisa smile, canine smile, full-denture smile. All the 3D smiling models were superimposed on the corresponding neutral one and point-to-point root mean square (RMS) differences were computed. Labial surface areas in rest position and during each smile were calculated as well, together with the percentage modification in different types of smile. RMS values (facial and labial models), labial surface areas and percentage modifications were compared through ANCOVA tests to verify possible statistically significant differences according to sex and type of smile (p < 0.05). Intercanthal labial width was considered a covariate. RMS values progressively increased from Mona-Lisa to full-denture smile; statistically significant differences were found among all types of smiles, both for facial and labial models (p < 0.05), while no statistically significant sex and sex × smile interactions were found (p > 0.05). Labial surface and percentage of modification showed statistically significant differences according to both sex and type of smile (p < 0.05). The study provides a novel contribution to the field of sexual dimorphism in smiling. Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Comparison of 3D Scanning Versus 2D Photography for the Identification of Facial Soft-Tissue Landmarks

Background:

Three dimensional facial scanning is an innovation that provides opportunity for digital data acquisition, smile analysis and communication of treatment plan and outcome with patients.

Objectives:

To assess the applicability of 3D facial scanning as compared to 2D clinical photography.

Materials & Methods:

Sample consisted of thirty Caucasians aged between 25 and 50 years old, without any dentofacial deformities. Fifteen soft-tissue facial landmarks were identified twice by 3 observers on 2D and 3D images of the 30 subjects. Five linear proportions and nine angular measurements were established in the orbital, nasal and oral regions. These data were compared to anthropometric norms of young Caucasians. Furthermore, a questionnaire was completed by 14 other observers, according to their personal judgment of the 2D and 3D images.

Results:

Quantitatively, proportions linking the three facial regions in 3D were closer to the clinical standard (for 2D 3.3% and for 3D 1.8% error rate). Qualitatively, in 67% of the cases, observers were as confident about 3D as they were about 2D. Intra-observer Correlation Coefficient (ICC) revealed a better agreement between observers in 3D for the questions related to facial form, lip step and chin posture.

Conclusion:

The laser facial scanning could be a useful and reliable tool to analyze the circumoral region for orthodontic and orthognathic treatments as well as for plastic surgery planning and outcome.

Facial Mobility after Maxilla-Mandibular Advancement in Patients with Severe Obstructive Sleep Apnea Syndrome: A Three-Dimensional Study

Introduction. The functional results of surgery in terms of facial mobility are key elements in the treatment of patients. Little is actually known about changes in facial mobility following surgical treatment with maxillomandibular advancement (MMA). Objectives. The three-dimensional (3D) methods study of basic facial movements in typical OSAS patients treated with MMA was the topic of the present research. Materials and Methods. Ten patients affected by severe obstructive sleep apnea syndrome (OSAS) were engaged for the study. Their facial surface data was acquired using a 3D laser scanner one week before (T1) and 12 months after (T2) orthognathic surgery. The facial movements were frowning, grimace, smiling, and lip purse. They were described in terms of surface and landmark displacements (mm). The mean landmark displacement was calculated for right and left sides of the face, at T1 and at T2. Results. One year after surgery, facial movements were similar to presurgical registrations. No modifications of symmetry were present. Conclusions. Despite the skeletal maxilla-mandible expansion, orthognathic surgical treatment (MMA) of OSAS patients does not seem to modify facial mobility. Only an enhancement of amplitude in smiling and knitting brows was observed. These results could have reliable medical and surgical applications.

A finite element model of the face including an orthotropic skin model under in vivo tension

Computer models of the human face have the potential to be used as powerful tools in surgery simulation and animation development applications. While existing models accurately represent various anatomical features of the face, the representation of the skin and soft tissues is very simplified. A computer model of the face is proposed in which the skin is represented by an orthotropic hyperelastic constitutive model. The in vivo tension inherent in skin is also represented in the model. The model was tested by simulating several facial expressions by activating appropriate orofacial and jaw muscles. Previous experiments calculated the change in orientation of the long axis of elliptical wounds on patients' faces for wide opening of the mouth and an open-mouth smile (both 30(o)). These results were compared with the average change of maximum principal stress direction in the skin calculated in the face model for wide opening of the mouth (18(o)) and an open-mouth smile (25(o)). The displacements of landmarks on the face for four facial expressions were compared with experimental measurements in the literature. The corner of the mouth in the model experienced the largest displacement for each facial expression (∼11-14 mm). The simulated landmark displacements were within a standard deviation of the measured displacements. Increasing the skin stiffness and skin tension generally resulted in a reduction in landmark displacements upon facial expression.

Facial mimicry after conservative parotidectomy: a three-dimensional optoelectronic study

Facial nerve paralysis is one of several possible complications following conservative parotidectomy. To assess three-dimensional facial movements non-invasively in patients with unilateral facial palsy following parotidectomy for benign tumours, the three-dimensional coordinates of 21 soft-tissue facial landmarks were recorded in 32 patients (21 HB I, 5 HB II, 6 HB III-IV; 3 months post-surgery follow-up), and 40 control subjects, during the performance of facial movements (smile, 'surprise', eye closure, single eye closure). For all symmetric animations, control subjects had larger total mobility than patients; mobility progressively decreased in patients with larger clinical grades. For asymmetric eye closures, HB I patients and control subjects had similar total movements, while HB II patients had smaller movements, especially for the paretic side eye closure; smaller total movements were found in HB III-IV patients. The method allowed the quantitative detection of alterations in facial movements. Significant differences between patients and control subjects in the magnitude and asymmetry of movements were found.